ai-agents-chat-template-overri-chat-template-for-gpt-oss-models-ignores-user-prov-19d5d3ce

THEN Update the `get_system_message()` call in `vllm/entrypoints/openai/serving_chat.py` to pass `chat_template_kwargs` and any user-specified model identity. Also ensure `get_system_message()` in `vllm/entrypoints/openai/parser/harmony_utils.py` accepts and uses these parameters instead of falling back to hardcoded defaults.

```python
def get_system_message(model_id: str, chat_template_kwargs: dict = None):
    if chat_template_kwargs and 'model_identity' in chat_template_kwargs:
        model_identity = chat_template_kwargs['model_identity']
    else:
        model_identity = 'default_gpt_oss'
    # ... rest of function
```
Then update the call site: `system_message = get_system_message(model_id, chat_template_kwargs=request.chat_template_kwargs)`